N-acyl piperazines and piperazino alkylamides of n-acyl piperazines of polybasic acids, methods of producing the same, and methods of employing the same as corrosion inhibitors



United States Patent Claims. (Cl. 252-855) This application is adivision of application Ser. No. 857,500, filed Dec. 7, 1959, now US.Patent No. 3,167,554.

This invention relates to methods of inhibiting corrosion of ferrousmetals in the presence of fluids such as brines and oils and is ofparticular utility in the inhibition of corrosion of casings, liners,tubing and rods employed in petroleum oil wells.

This invention is also directed to novel compositions of matter whichare useful for such purposes and for other forms of corrosion inhibitionas well as for other uses.

It is one of the objects of my invention to prepare amino amides frompiperazine or substituted piperazines and high molecular weightpolybasic carboxylic acids.

I have found that a composition of matter having constitutional FormulasI or II or III or mixtures of two or more thereof will give stabledispersions in saline waters and will inhibit corrosion of ferrous metalin contact with such saline waters.

CHz-CE: '0'

C-R C 2C 2 m 11 That is, the piperazine alkylamide of the polybasicacid.

Formula III:

That is, the piperazino alkyl amide of N-acyl (polybasic acid)piperazine.

Each of the above compounds is an amino amide of a polycarboxylic acid,in which there is at least one amino nitrogen, either primary, secondaryor tertiary, for each amido nitrogen. In each of the aboveconstitutional formulas mi:n=y+Z, and is equal to at least 2 and is notmore than 4, where y and z are each at least 1 and x is at least 2 andnot more than 4. These compounds may com tain in admixture none or onlyminor amounts of compounds in which m, n, and y+z are in excess of 4. Inthe above constitutional formulas, O=CR is an acyl radical in which Rcontains from 17 to 21 carbon atoms, and R is chosen from the groupconsisting of hydrogen, alkyl, amino alkyl or hydroxyalkyl groups inwhich the alkyl radical is of not more than four carbon atoms.

The preferred values of n are 2 or 3, and the best compounds for use ininhibiting corrosion, as will be discussed below, have been those inwhich the n value is predominantly 2 with small amounts of those havingvalues of n=3, and in which the polyacyl radical is obtained bypolymerization of unsaturated fatty acids having C to C carbon atomsincluding the carboxyl carbon.

Such dibasic acid polymers are suitably obtained by well knowntechniques for the polymerization of unsaturated fatty acids and havebeen described in US. Letters Patents, and literature, to whichreference is here made. These are included only by way of illustrationand example and not as limitations of my invention. The method offorming polybasic acid does not form a part of this invention.

Specific di or polycarboxylic acids of this type have been described byT. F. Bradley et al. (Ind. Eng. Chem., vol. 32, page 694; vol. 32, page804; and vol. 33, page 86). Commercially, such products are readilyavailable from processes described, for instance, in US. Patent2,482,761 (C. G. Goebel), also U.S. Patents 2,793,219 and 2,793,220 (F.O. Barrett and C. G. Goebel). Such di and polycarboxylic fatty acidsneed not be of high purity to produce the compounds of my invention andmay contain some of the unreacted monocarboxylic acids. Unrefined,undistilled acid mixtures as produced by this thermal polymerizationprocess are generally satisfactory. For example, such products asproduced in US. Patent 2,793,220, Examples 1 to 7, or US. Patent2,793,219, Example 9, without further refinements such as distillationto remove the unreacted residual monocarboxylic acids can be utilized,even though the relatively monomer free form of dimer, trimer andpolymer acids are preferred.

These processes cause the polymerization of unsaturated fatty acids of Cto C carbon atoms, or esters thereof, of vegetable oils, marine oils,animal oil or oil of synthetic origin. For example, such polybasic acidsmay be obtained by polymerization of oleic, linoleic, ricinoleiclinolenic and linoelaidic and other singly or doubly unsaturated fattyacids of suitable chain length, or of their esters.

The structure of these polybasic acids has not been fully elucidated,nor is it fully established whether they are polymerized by a freeradical or by a Diels-Alder mechanism.

The following is one possible scheme of these structures, assuming aconjugated doubly unsaturated acid. But it may not be the exclusivestructures, and is given only for illustrative purposes.

The dimeric polymers:

The tetramer form would require a further reaction where the double bondor the reactive acid and trimer combine to form a tetramer presumablyhaving a three ring structure.

For purposes of distinction from other polybasic acids of high molecularweight, the polymer acids referred to above are characterized in thateach pair of carboxyl group is separated by relatively long carbon tocarbon chains.

For example, these acids may be obtained by suitable 0 polymerization oflinoleic acid to produce polymers con- 3 monomer, i.e., linoleic acid,as referred to in the Fischer US Patent 2,805,201.

Another polymeric acid is the dimer acid sold by Emery Industries, Inc.,as Emery 30798, composed of about 95% dimer acid (dilinoleic acid),about 4% of trimer acid (trilinoleic acid) and 1% of monobasic acid(linoleic acid). A very suitable and low cost raw material is theby-product from the caustic fusion of castor oil for the production ofsebacic acid.

The diamines employed in the amidification of the above polybasic acidsare preferably the dibasic heterocyclic diamines and preferably thepiperazines and substituted piperazines having the constitutionalformula Formula IV:

Ulla-C 2 /NH CH2-CH2 HgN- CHI-C Hr-N N-(3-aminopropyl) piperazineCHr-CH:

l-(methyl)-4-(3-aminopropyl) piperazine CHg-CH,

NCHa

OHa-CH:

1,4-piperazine bis propylamine CHz-CHr l-(p-hydroxyethyl)-4-(3-aminopropyl) piperazine GHQ-CH2 HzN-CHr-CHz-CHr-N The ethyl propyland butyl homologues of the above listed compounds may be used. Mixturesof two or more of the above may also be employed in forming the aminoamide of the polybasic acids of my invention.

I may use the unpurified commercial products containing mixtures of oneor more than one of the above piperazine and the alkyl, aminoalkyl, andhydroxyalkyl substituted piperazines, or purify them to separate someorall of the several components into any desired degree of purity andemploy such fractions to produce the amino amides of my invention. Themethod of forming the piperazine or substituted piperazine is not a partof the invention of this application.

The compounds of my invention may be prepared, for

example, by way of further description and not as a limitation, by thefollowing procedures.

I react the piperazine or substituted piperazine with the polybasic acidreferred to above, employing more than one mole of the piperazine orsubstituted piperazine per carboxyl radical, to cause amidification ofonly one of the amine nitrogens of the piperazine or substitutedpiperazine employed. It is desired that the resultant amide be an aminoamide wherein there is at least one amino nitrogen for each amidenitrogen. The reaction results in the formation of the compound FormulaI when the substituent R in Formula IV is hydrogen, alkyl or hydroxyalkyl, or Formula II or Formula III or a mixture of Formula II and IIIwhen the substituent R in Formula IV is hydrogen, alkyl alkylamine orhydroxyalkyl and the substituent R is alkylamine.

Where the piperazine is substituted by an hydroxyalkyl group, theamidification is carried out under conditions to inhibit esterificationof the hydroxyl group b the carboxyl group. The products producedcontain but a few percent, generally less than 5% by weight, of theesters.

In order to obtain the most desirable water or brine dispersibility, theamidification reaction is preferably carried to completion as far aspracticable in order to amidify the available carboxyl-carbonyl groups.The unreacted polybasic acid is not dispersible in water or brine, andin order to obtain as little unreacted acid as is practicable, thereaction is carried out with an excess of the piperazine or substitutedpiperazine.

These conditions of reaction will be more fully understood by thoseskilled in the art from the examples given below.

Such compounds are readily soluble or dispersible in colloidal state inwater and in heavy brine and in aromatic and oxygen bearing solvents,such as, for example, toluol, xylol, ethyl alcohol, methyl alcohol,isopropyl alcohol, ether alcohols and polyglycols and other conventionaloxygenated solvents, to give dispersions, including within the termmolecular dispersions, i.e., solutions and colloidal dispersions, whichare stable, i.e., will not precipitate at ambient temperatures and ateven high temperatures, such as the boiling point of the dispersion.They have a low viscosity, do not gel, and foam only moderately. Theyare effective surfactants, being cationic in nature.

While I do not Wish to be bound by any theory of the action of mycompounds of my invention in inhibiting corrosion of ferrous metals inthe presence of brines and oils, the following is given as anexplanation thereof:

The compound of my invention preferentially Wet ferrous metals, toprovide tightly adhering, continuous hydrophobic coatings. The filmproduced when the metal is wetted is resistant to stripping by thesaline waters or oil. But the film, being oleophylic, is easily wettedby oil; and thus, in the presence of oil and brine, the metal, whenwetted by the inhibitor, is also coated by a tightly adhering oil filmwhich further protects the metal. The surfactant acts as the primer orundercoat for the oil film. The oil will not strip the film from themetal because of the low solubility of the compounds in oil such aspetroleum oil.

The compounds are dispersible in water and brine in concentrations whichrange up to 10,000 parts per million of the water, depending on thecompounds employed, and the dispersions are not precipitated bymonovalent ions such as Na or K or by polyvalent cations such as calciumor magnesium, and thus give stable dispersions in brines usually formedin oil wells. Additionally, because of their basicity, they are notprecipitated by the acidity often found in such oil well fluids, as forexample that arising from H 8 or CO present in the oil well fluids.

Solutions in both brine and water of the compounds described, whentested at a concentration of 0.5% by weight of the aminoamides of myinvention, or certain of the water soluble salts of these compounds,exhibited a reduced surface tension of approximately from 32 to 42dynes/ cm. at 25 C. as compared to distilled water of 72 dynes/cm. whenmeasured on a DuNouy Surface Tensiometer.

It should be pointed out that, owing to the good water dispersibility ofthe bases themselves, salts with water solubilizing acids need not beformed. For practical application, however, the following acids areenumerated as examples of acids that are suitable to retain the waterand brine solubility or improve the stability of the dispersion wherethe salts of such bases rather than the bases themselves are preferredto be used as the corrosion inhibitors:

Alkylmanocarboxylic acids: Formic, acetic, propionic,

butyric, isobutyric, valeric acids.

Hydroxyalkylcanboxylic acids: Glycollic, lactic, hydroxypropionic,hydroxybutyric acids.

Di and Polycarboxylic acids: Malonic, succinic, glutaric, aclipic,fumaric, maleic, citric, tartaric, gluconic, malic acids.

The neutralization of the amino amide described above may be carried outin a suitable solvent such as, for instance, aqueous alcoholic solution,to promote the removal of heat developed during neutralization andprevent side reactions such as amidification with the acids enumeratedabove. Such procedure is useful where hydrogen substituted amine groupsare available for reaction, and to inhibit possible reaction with doublebonds of the highly reactive unsaturated acids, such as crotonic acid,fumaric or maleic acid, where such acids are employed.

Acids other than the carboxylic or polycarboxylic acids can be resortedto in forming desirable salts of the amino amides described above.

The following examples are given by way of illustration and not as alimitation of my invention.

EXAMPLE 1 Preparation of bis-(piperazine ethyl) amide of dimer fattyacid Where R is fatty residue of dimer acid described below.

Into a 4,000 ml. resin reaction apparatus (Scientific Glass ApparatusCo., 14400) equipped with vacuum tight stirring assembly, thermometer,insulated funnel, Claisen distilling head connected to a distillatecollector and vacuum pump, is charged:

12 moles, equal to 1550.4 grams, aminoethyl piperazine (M.W. 129.2, sp.gravity 20 C. 0.984; refractive index 20 C. 1.4999; and a distillingrange at 760 mm. Hg of 214.8221.8 C.)

This was heated to 300320 F. with the electrical heating mantle, Whilemildly purging with nitrogen gas.

3 moles, equal to 1,749.6 grams dimer acid Emery 30798, referred toabove (acid value 192.4 and containing about 95% dimer acid, 4% trimeracid, and 1% monobasic acid, refractive index at 25 C. 1.4845),

were warmed separately to about 200 F. and were then added to theaminoethyl piperazine at 310-320 F. over a period of about 45 hoursthrough the insulated funnel. At this point, 45 ml. of distillate werecollected, and after an additional two hours of heating at the indicatedtemperature, the acid number had fallen below 6, and 80 ml. distillatehad collected. Heating under nitrogen atmosphere was continued for 6additional hours at this temperature, and after collecting 1 01 ml.distillate, the acid number had fallen to 2.7. Holding the temperatureat about 320 F., a vacuum was now applied, reducing the pressure insidethe reactor to 12 mm. Hg, gradually, so as to prevent excessive foaming.Within 3% hours, 725 grams of the 775 grams excess aminoethyl piperazinehad been removed, and the acid number had fallen further to 1.87. Aminor amount of aminoethyl piperazine appears to have complexed duringthe reaction, or was difficult to remove, as is also indicated by theyield of 2,466 grams, versus 2,417 grams theory. As will be seen inadditional examples, excess amine may be left in the product, or may bestripped only partially where desired. The resulting compound(substantially: bis (piperazinoethyl) amide of dimer acid) was a pale,amber, viscous, resinous liquid, with a viscosity of F. of 14,400 cps.,spindle 5, 20 rpm. Total nitrogen calculated as 10.4, was found to be10.94 by method of Kjeldahl. 50% of the above compound, 25% water, and25 isopropanol formed an easy to handle, clear liquid concentrate. 40grams of this concentrate dissolved in 960 grams water formed a hazy,stable, mildly foaming solution, having a viscosity of 4 cps, spindle 1,at 20 rpm. (Brookfield Synchro-Lectric viscometer). The surface tensionat 25 C. was measured at 35.6 dynes/cm.

The excellent corrosion protective properties of this compound and itssalts will be demonstrated below.

EXAMPLE 1-A The glycollic acid salt of the bis (piperazinoethyl) amideof dimer acid, as per Example 1, was prepared as follows:

There was then added at so as to avoid excessive heat development. Thetemperature was so held under F., although higher temperatures (belowtemperatures resulting in amidification) would not harm.

The salt had a solids content of about 50% and a pH of 5.5 and was aclear liquid. Experience has shown subsequently that a somewhat higherpH of about 6-8 will be preferable. This compound at the lower pHnevertheless gave outstanding corrosion protection, as may be seen fromthe table below.

EXAMPLE 2 Preparation of his [l-acyl (dimer acid)-4-melhyl] piperazineCH2CH2 CH2CH2 N-CHa CH2CHz CH2CH1 Where R is residue of dimer aciddescribed.

Into a 1,000 ml. 3 neck distilling flask, equipped with heating mantleand other accessories mentioned in Example 1, but with a hot waterjacketed reflux condenser, inserted between the flask and Claisendistilling head, is charged:

1.75 moles, equivalent to 175.3 grams of N-methylpiperazine (molecularweight 100.1; purity 99.5%; specific gravity at 20 C. 0.904); refractiveindex 20 C. 1.4 652; distilling range at 760 mm. Hg of 135.3142.6 C.(ASTM). This was heated while purging with nitrogen and adding 0.7 mole,equal to 408.2 grams of the previously warmed dimer acid described inExample 1.

In this case, addition can be made at as rapid a rate as permissible,since only the secondary amine group is reactive and polymerization intopolyamides of large chain length is not possible.

After 22 hours of reaction time of 264270 F., reaction had gone tocompletion to about 96%, and the small amount of excessN-methyl-piperazine still remaining in 7 the reaction product wasretained therein without distilling off. Much of the initially chargedexcess had been retained, as was determined by the final amineequivalent weight found by titration.

Theoretical amine equivalent weight based on original charge 266 Found280 A fully vacuum stripped compound would have the amine equivalentweight of about 374.

The resulting compound was a resinous, pale amber, viscous liquid, butsubstantially more fluid than the compound of Example 1.

50% of the above compound, 25% isopropanol and 25% Water formed an easyto handle, clear oil.

40 grams of this concentrate was then dissolved in 960 grams ofdistilled water, yielding a stable, hazy, moderately foaming solution,having a viscosity of 6 cps. and a surface tension of 33.5 dynes/crn. at25 C. A like concentration (0.5% actives) in brine was equally stable,similar in appearance, showed a viscosity of cps. and a surface tensionof 32.2 dynes/cm. at 25 C. The table below is indicative of itsexcellent corrosion protective properties.

EXAMPLE 3 Preparation of his [I-acyl (dimer acid)-4-beta hydroxy ethyl]pipcrazine CH -CH: o 0 011 -0112 N C-Ra-G-N N-CHz-CHrOH CHrC rt CHz-CH;

Into an apparatus as described in Example 2, but not equipped with thehot Water jacketed reflux condenser, was charged:

This charge was then heated to 320 F. while purging with nitrogen.Through the insulated funnel was then added:

0.7 mole equivalent to 408.2 grams of the dimer acid described inExample 1.

HO-CHrGHrN The dimer acid had been warmed to about 200 F. to improve itsflow. Addition of the dimer acid was made over a period of 4 /2 hours,and at the end of this period, the reaction had proceeded to in excessof 50% completion. Heating under constant agitation and purging withnitrogen was continued at this temperature (320322 F.) at which timeover 22 grams of distillate had been collected, while the acid numberhad fallen to 4.6. The excess hydroxyethyl piperazine was not removed.There was obtained a yield of 601 grams. (Theory: 610.8 grams.) Theresultant product was of a light amber, viscous liquid, having an amineequivalent weight of 284 (theory: 290.8, including the excess aminecharged). The close values on amine equivalent of practice versus theoryobtained by titration indicated that substantially only the hisN-acylated hydroxy ethyl piperazine had formed and that esterificationwas held to the minimum. Subsequent scanning of the compound on aninfrared spectrophotometer showed only trace quantities of ester presentas evidenced by a minor peak at 5.74 microns, and a massive peak at6.056.1 microns typical for amide.

As in the previous case, there was prepared a 50% solution in alcoholand water, and the clear liquid resulting was introduced into distilledwater and brine solution to examine solubility, viscosity, andperformance as to surface activity.

An 0.5% by weight solution (active basis) dissolved in distilled Waterto give a mildly foaming opalescent to hazy solution, having a viscosityof 5 cps. and a surface tension of 42.8 dynes/cm. at 25 C. Solution inbrine showed excellent stability as well; was hazy in appearance,conformed to a viscosity of 6 cps. and gave a surface tension of 32.4dynes/cm., much lower than the surface active properties obtained indistilled water. Again, the powerful corrosion protective properties maybe noted in the accompanying tables.

EXAMPLE 4 Preparation of his (I-methyl piperazino propyl) amide of dimeracid Into a 1,000 ml. 3 neck flask, equipped as in Example 2, butwithout the insulated funnel, was charged:

/2 mole, equivalent to 291.6 grams dimer acid as used in Example 1, and

1.1 mole, equivalent to 173.0 grams of l-methyl 4-(3- aminopropyl)piperaziue (refractive index 1.4812 at 22 C.; boiling point 225 C. at760 mm. Hg),

the amine having been derived by reaction of acrylonitrile upon Nmethyl-piperazine, followed by reduction in methanol in the presence ofliquid ammonia and Raney nickel catalyst (under hydrogen pressure).

Both reagents were charged at once and heated to 330 F. gradually, overa period of 9 hours and held there for an additional 4 hours. At thispoint, the acid number had fallen to a value of 4.9, and a vacuum wasthen applied to a reduced pressure of 4 mm. Hg for 2 hours, to strip theslight excess amine. The acid number had fallen further to 1.9. A yieldof 427 grams was obtained, comparing with 'a theoretical yield of 430.6grams. Total nitrogen by method of Kjeldahl was found to be 9.48% asagainst theory of 9.76%.

The product was a light amber, viscous oil, materially more fluid thanthe compound of Example 1. An 0.5% by weight solution of this compoundwas hazy, mildly foaming, and stable, and had a sunface tension of 37.5dynes/ cm. and a viscosity of 5 cps, and generally resembled thecompound of Example 1, except for its lower viscosity in the form,measured as 8,300 cps, spindle 4, 20 rpm, Brookfield Synchro-Lectricviscometer at 100 F.

EXAMPLE 5 Preparation of poly (piperazino ethyl) amide of crude polymeracid described below Into an apparatus as described in Example 1 werecharged:

8 moles, equivalent to 1,033.6 grams of N-(Z-aminoethyl) piperazine. Thetemperature was then brought to 320 F. and there was added over a periodof about 5 hours 4 times the equivalent weight of 381 (as determinedfrom an acid number of 147.2) of the polymerized linoleic acid obtainedas the co-product in the manufacture of sebacic acid by caustic fusionof castor oil, described in previous pages and available from Rohm &Haas Company as Acid VR1. It is the high boiling material remainingafter distillation of sebacic acid, capryl alcohol and other morevolatile acids. It is understood to be a polymerized linoleic acidconsisting principally of dimers, trimers and tetramers, etc. Thematerial has an average molecular weight in the range of 1000,containing fractions of molecular weight in the range of 300- 1300. Theiodine value ranges from about 40-70. The

acid number is in the range of 145l80. The average functionality isequal to about two carboxylic groups per molecule, and behaves like a dibasic acid in the amidification reaction of this example.

After 6 additional hours following completion of addition, the acidnumber had fallen to a value of 4.0. The batch was then partiallystripped to an amine equivalent weight of 219 by titration, leavingabout 217 grams of the excess aminoethyl piperazine in the finalproduct. This checked well with the yield of 2,178 grams obtainedagainst theory of 1,968 grams of product expected after completestripping and the theoretical amine equivalent weight of the partiallystripped batch calculated as 215.

The resultant compound was dark brown in color, had a final acid valueof 2.4, and gave a viscosity of 21,800 cps., spindle 5, at 10 r.p.-m.,at 100 F.

An 0.5% by weight solution of this compound in distilled water gave asurface tension of 34.5 dynes/cm. at 25 C. and a viscosity of 5 cps.,while an 0.5% solution in brine registered a surface tension of 32.4dnyes/ cm. at 25 C. and showed a viscosity of 6 cps. Both solutions werestable, hazy in appearance and mildly foaming. The compound otherwiseresembled in all respects the compound of Example 1.

Example 6 Percent N-amino ethyl piperazine 38 N-hydroxy ethyl piperazine12 High molecular weight complexes of the above 40-45 Minor quantitiesof other amines.

This mixture of the crude piperazine derivatives had an amine equivalentweight of 59 by titration. The amine was now heated to 320 F. and,proceeding as in Example 1, there were slowly added at this temperature5 times the equivalent weight, equal to 1,882.5 grams of the VR 1 acidas described above and having an acid value of 149. The reaction masswas brought to an acid number of 4.8 after heating for 12 hours at toptemperature, and the dark brown substance gave an amine equivalentweight of 248 upon titration. The viscosity was somewhat higher thanthat obtained with Example 5.

This compound was now dissolved in isopropyl alco- 1101 and neutralizedwith 70% glycollic acid to a pH of about 7, whereupon it was furtherdiluted to actives (based upon the salt) with water. The brown, lowviscosity solution readily dissolve in water or brine to give moderatelyfoaming stable solutions exhibiting pronounced surface activeproperties. An 0.5% solution of this glycollic acid salt in brine gave asurface tension of 36.8 dynes/cm. at C., a value which proved almostidentical to the value found with the similar compound of Example 5. Thecompound of Example 5 as the glycollic acid salt showed, however, evenhigher solubility in brine, producing perfectly clear solutions in brineat 0.5 concentrations.

Where this greater solublity in brine is desired, one may increase theexcess of the crude piperazine derivative initially charged based uponequivalent values of amine versus acid used in the initial condensationreaction. From the table below and practical experience noted, one willreadily deduce the outstanding effectiveness of this compositiondescribed in Example 6.

Where lighter colored products are desired than obtainable with thecrude co-product used in Example 6 as the piperazines, the co-productcan be bleached with bleaching clays and followed by filtration, orflask dis- J10 tilled to produce like products, but containing 60-70% N-aminoethyl piperazine and about 840% N-hydroxyethyl piperazine, withless than 10% of high molecular Weight homologues and only small amountsof other amine contaminants. This may be used in place of thepiperazines in Example 6.

In the above Example 6, the resultant product may contain a mixtureincluding poly [l-acyl (polymer acid) -4- beta hydroxy ethyl] piperazinesimilar to the form of compound produced in Example 3, and poly(piperazine ethyl) amide of the polymer acid similar to Example 4, andthe piperazino ethyl amide of N-acyl (polymer acid) hydroxy ethylpiperazine by the amidification of the polymer acid by both the hydroxyethyl piperazine and the amino ethyl piperazine. Where the poly acid ispredominantly dimer, the first two compounds will be a his compound, theacyl radical being the dilinoyl radical, and the third named compoundmay be illustrated by the following formula:

Where R as above is the carbon chain radical of the polymer acidemployed. Higher molecular weight amine complexes also a-midify thepolybasic acid to form high molecular weight amino amides. As in theprevious examples, in the case of the dilinoleic acid, R is C due to theamidification of the dilinoleic acid. In all of the above examples thepresence of tetramer and trimer forms of the polybasic acid will giverise to minor amounts of higher molecular weight complexes due to theamidification reactions with the three carboxyl groups of the trimer orfour carboxyl groups of the tetramer.

The amino amides of the polybasic acid in which the monomer acyl radicalis C to C are extremely effective corrosion inhibitors in the presenceof water or brines and are equally effective in water and brinescontaining H S or CO acidity, and will also inhibit corrosionetfectively in the presence of petroleum gases and oils. They are thusof utility in the inhibition of corrosion in oil wells and petroleumpipe lines and in storage equipment. They are also useful for anyferrous metal corrosion inhibition, particularly protection of corrosionof ferrous metals in contact with waters containing salts, for example,the salts of the alkali metals or alkaline earth metals.

The effectiveness of the compounds of my invention as corrosioninhibitors will appear from the following:

EXAMPLE 7 The brine solution used to test the corrosion inhibition hadthe following composition:

Percent Distilled water 95.8

Sodium chloride 4.0

and

Calcium chloride 0.2

The following procedure was used to determine the effectiveness of thecompounds enumerated above:

Polished steel rods 6 long, A2 diameter (S.A.E. 1018) are finished offwith fine emery cloth and are then stored in pentane until ready foruse. Two test specimens are then accurately weighed and mounted side byside on ployed as the hydrocarbon phase).

the head of a rocking autoclave having a little over 4 liter capacity.3,900 ml. of a well evacuated 3 /2 NaCl solution in tap Water is nowcharged into the autoclave, along with 200 ml. of an evacuated kerosene(em- The corrosion inhibitor was now added, using 6.8 parts per million(ppm) where the salts of the amino amides described above were thecompounds tested, and 5.7 ppm. where the amino amide bases themselveswere used. The autoclave was then closed and purged with CO finallycharged with 20 p.s.i.g. pressure of CO and heated under pressure for 24hours.

The rods are then removed again, washed and weighed to determine theweight loss, if any.

This test procedure is basically the procedure described in USP2,805,201, Paul W. Fischer (see column 3). The tremely high in water.

salt content was increased and the inhibitor concentration reduced toincrease the severity of the test and bring results closer to extremeconditions existing in the fields.

The eificiency is determined by the following formula:

(Wtwn x W1 Efliciency:

g0 annulus, the c rwJlii commercially of interest. Preferred arecompounds which show at least 95% efliciency by the above test. Thedegree of effectiveness of the compounds of my invention is shown by the97.4% to 99.8% etficiency scored by these compounds in the above test,as shown in the table.

Because of their dispersibility in water and stability in oil wellbrines and low solubility in petroleum oils, they may be used with highdegree of effectiveness where the well is producing water and even wherethe out is ex- They may also be used with great ettectiveness in wellswhich do not produce water or only insubstantial amounts thereof.

Thus, in gas and condensate Wells having an open annulus, the materialmay be inserted through the open annulus as a water dispersion orsolution in an organic solvent. Addition may be made over a period oftime until the test of the effluent liquid shows a low iron content, andthereafter pc riodic 2 dditions may he made.

In gas and cc n lensate v ells which do not have an open slug rrethodmay be emclfil (llSpt-Iol u or solution in an organic solvent of theilhlbltOI' is in ected into the well and the well shut in for a sumcielength of time to allow the dispersion to reach the bottom.

ploycd. A vol ne of 5 In flowing or pumping wells, which either are dryoil TABLE I Milligram Specimen, Conccnweight loss or gain PercentInhibitor Tested tratiou rg in ppm. U011 I. Test II. Repeat TestFlank-no inhibitor -1, 244 --l, 354 9 Compound Example 1 (Base) 5. 7 -289 3 Compound Example 1-A (Salt, Glyc0llute) a 3 -16 9 8 Compound Example2 (Base) 5. 7 +1. 8 11 4 1 Compound Example 3 (Base) 5. 7 -18 6 CompoundExample 2 (Salt, Acetate) s. s -33 9 4 Compound Example 6 (Salt,Glycollate) a s -5 4 +16 8 99.5 Bis (Piperazino ethyl) Amide of AzelaicAcid alt, Acetate 6 8 -992 3. Bis (Piperazino ethyl) Amide of DodecenylSuccinic acid (Salt, Acetate). 6.8 882 -910 08 Attention is called tothe specific nature of the chain length of the polybasic acids asaflecting the performance producers or have low or high water cuts, thewells may be protected against corrosion by injecting the waterdispersion or solution in an organic solvent of the inhibitor, eitherperiodically or continuously, until the iron content in the circulatingfluid has been reduced to the desired concentration. Thereafter theintroduction may be made in Examples 1-6 as compared to the amino amidesof periodically.

dibasic acids of smaller chain length, i.e., lower molecular weight,amino amide analogues of such lower molecular weight acids were preparedand similarly tested. Thus, amides formed from the piperazines accordingto Formula IV to give compounds according to Formulas I to III,

where the acyl group is azelate, adipate, sebacate, ordodecenylsuccinate, derived by amidification of azelaic, adipic, sebaic,or of dodecenylsuccinic acid or dodecenylsuccinic anhydride bypiperazines of Formula IV, produce amino amides which are of such loworder of corrosion inhibition as not to be of practical value ascorrosion inhibitors, particularly when considered for use in oil wells.

Thus, for example, the acetate salt of his (piperazino ethyl) amide ofazaleic acid and the acetate salt of bis (piperazino ethyl) amide ofdodecenylsuccinic acid, when tested according to the test procedure ofExample 7, gave the results shown in Table I.

Experience in the field, particularly in the protection of The additionmay be made by continuous injection into the annulus or by the slugmethod described above.

In making the water dispersions, brines separated from the crude oil maybe employed to dilute the concentrate.

The utility of the inhibitors previously described will appear from thefollowing examples.

EXAMPLE 8 The composition of matter of Example 6, in the form of theglycollic acid salt, was dissolved in one part of isopropyl alcohol and3 parts of water to form a solution containing 20% by weight of thesalt. This solution was diluted with several barrels of water andinjected by the slug method into a pumping well producing 800 barrelsper day of fluid containing 93% brine. The amount of inhibitor injectedper day was equal to 10 parts per million of the glycollic acid saltbased on the total mixed fluid of brine and oil produced; that is, atotal of about 2.8 pounds of the glycollic acid salt was injected intothe well each day, using the slug method. Prior to the in- 011 fieldeqmpment and m oil wells has shown that the jection of the inhibitor theiron content of the 800 barrels higher the efliciency by the above testthe less the amount of inhibitor required and the longer is the periodof effectiveness, and the greater the degree of inhibition. In fact, inoil field practice, it has been found that an efficicncy of at least 90%is desirable for an inhibitor to be longer than six months.

equalled 4 pounds by chemical analysis. After a few days treatment thetotal iron content of the 800 barrels produced in each day was only 0.75pound. This low iron loss continued for the period of test, which was aperiod A portion of that iron loss con- 13 tained in the effluent aftertreatment must be accounted for by the normal iron content of the oiland brine produced by the formation.

EXAMPLE 9 Another well producing 300 barrels per day of oil and brinecontaining about 85% brine was similarly treated, using, however, 11.75parts per million; that is, about 1.23 pounds of the glycollic acid salteach day. Before treatment the iron content of the 300 barrels producedeach day was 3.45 pounds of iron, and after treatment the iron contentof the 300 barrels produced each day was only 0.46 pound per day.

The term consisting essentially of as used in the definition of theingredients present in the compositions claimed is intended to excludethe presence of other materials in such amounts as to interferesubstantially with the properties and eharacterisics possssed by hecomposition set forth but to permit the presence of other materials insuch amounts as not substantially to affect said properties andcharacteristics adversely.

While I have described particular embodiments of my invention, it shouidbe understood that various modifications and adaptations thereof may bemade within the spirit of the invention as set forth in the appendedclaims.

I claim:

1. A method of inhibiting corrosion of ferrous metals exposed tocorrosive agents normally present in a well producing petroleumhydrocarbons, which comprises introducing into said well a corrosioninhibiting composition of matter consisting essentially of a compoundchosen from the group consisting of N acyl (polybasic acid) piperazineand water dispersible salts thereof, the piperazino alkylamide of apolybasic acid and water dispersible salts thereof, and the piperazinoamide of a polybasic acid and water dispersible salts thereof, the acylradical of said polybasic acid corresponding to the formula where Rcontains from 17 to 21 carbon atoms and n is at least 2 and is not morethan 4, and in which the R radical contains carbon-carbon chains thatseparate the (3:0 carbonyl groups, each carbonyl group of said polybasicacid being amidified,

2. The method of claim 1, in which the compound is an amino amide of apolymer of an unsaturated fatty acid having an unsaturated fatty acidradical of 17 to 21 carbon atoms.

3. The method of claim 2, in which the polybasic acid consistsessentially of the dimer of linoleic acid.

4. The method of claim 2, in which the polybasic acid consistsessentially of a mixture of the dimer and trimer of linoleic acid.

5. The method of inhibiting corrosion of ferrous metals exposed tocorrosive agents normally present in a well producing petroleumhydrocarbons, which comprises introducing into said well a corrosioninhibiting composition of matter consisting essentially of a compoundchosen from the group consisting of N-acyl (polybasic acid) piperazinoof the formula and water dispersible salts thereof, a piperazinoalkylamide of a polybasic acid according to the formula and waterdispersible salts thereof, and a piperazino alkylamide of N-acyl(polybasic acid) piperazine, according to the formula and waterdispersible salts thereof, in which, in each formula, there is at leastone amino nitrogen for each amide nitrogen and in which m, n, y+z areeach equal to at least 2, y and z are each at least 1, and x is at least2 and not more than 4, and in which R contains from 17 to 21 carbonatoms and R is chosen from the group consisting of hydrogen, alkyl,amino alkyl and hydroxyaikyl group in which the above alkyl radical inthe above alkyl and substituted alkyl groups are each of not more than 4carbon atoms.

6. The method of claim 5, in which the amino amide is the amino amide\of a polymer of an unsaturated fatty acid having an unsaturated fattyacid radical of 17 to 21 carbon atoms.

7. The method of claim 6, in which the polybasic acid consistsessentially of the dimer of linoleic acid.

8. The method of claim 6, in which the polybasic acid consistsessentially of a mixture of dimer and trimer of linoleic acid.

9. The method of inhibiting corrosion of ferrous metals exposed tocorrosive agents normally present in a well producing petroleumhydrocarbons, which comprises introducing into said well a corrosioninhibiting composition of matter consisting essentially of a compoundchosen from the group consisting of his (piperazino ethyl) amide ofdimer of a C to C unsaturated faty acid and its water dispersible salts.

10. The method of inhibiting corrosion of ferrous metals exposed tocorrosive agents normally present in a well producing petroleumhydrocarbons, which comprises introducing into said well a corrosioninhibiting composition of matter consisting essentially of a compoundchosen from the group consisting of bis [l-acyl (dimer) 4-rnethyl]piperazine and its water dispersible salts, wherein the (dimer) is adimer of the acid radical of a C to C unsaturated fatty acid.

11. The method of inhibiting corrosion of ferrous metals exposed tocorrosive agents normally present in a well producing petroleumhydrocarbons, which comprises introducing into said Well a corrosioninhibiting composition of matter consisting essentially of a compoundchosen from the group consisting of his [l-acyl (dimer) 4-beta hydroxyethyl] piperazino and its water dispersible salts, wherein the (dimer)is a dimer of the acid radical of a C to (I unsaturated fatty acid.

12. The method of inhibiting corrosion of ferrous metals exposed tocorrosive agents normally present in a well producing petroleumhydrocarbons, which com prises introducing into said well a corrosioninhibiting composition of matter consisting essentially of a compoundchosen from the group consisting of his (l-methyl piperazino propyl)amide of dilinoleic acid and water dispersible salts thereof.

13. The method of inhibiting corrosion of ferrous metals exposed tocorrosive agents normally present in a well producing petroleumhydrocarbons, which comprises introducing into said well a corrosioninhibiting composition of matter consisting essentially of a compoundchosen from the group consisting of amido amides and the waterdispersible salts of amido amides, and amido amides consistingessentially of a mixture of poly [l-acyl (polymer acid) 4-betahydroxyethyl] piperazine, bis (piperazino ethyl) amide of polymer acid,and piperazino amide of N-acyl (polymer acid( hydroxyethyl piperazine,wherein (polymer acid) is a polybasic acid of which the acyl radicalcorresponds to the formula (O=CR) where R contains 17 to 21 carbon atomsand n is at least 2.

14. The method of inhibiting corrosion of ferrous metals exposed tocorrosive agents normally present in a Well producing petroleumhydrocarbons, which comprises introducing into said well a corrosioninhibiting composition of matter consisting essentially of a compoundchosen from the group consisting of amido amides and the waterdispersible salts of amido amides, said amido amides consistingessentially of a poly (piperazino ethyl) amide of polymer acid chosenfrom the group consisting of the dimer, trimer and tetrarner of the C toC unsaturated fatty acids and mixtures thereof.

15. The method of claim 14, in which the polymer consists essentially ofthe dimer of the linoleic acid.

References Cited by the Examiner UNITED STATES PATENTS LEON D. ROSDOL,Primary Examiner.

0 ALBERT T. MEYERS, SAMUEL H. BLECH,

Examiners.

H. B. GUYNN, Assistant Examiner.

1. A METHOD OF INHIBITING CORROSION OF FERROUS METALS EXPOSED TOCORROSIVE AGENTS NORMALLY PRESENT IN A WELL PRODUCING PETROLEUMHYDROCARBONS, WHICH COMPRISES INTRODUCING INTO SAID WELL A CORROSIONINHIBITING COMPOSITION OF MATTER CONSISTING ESSENTIALLY OF A COMPOUNDCHOSEN FROM THE GROUP CONSISTING OF N ACYL J(POLYBASIC ACID) PIPERAZINEAND WATER DISPERSIBLE SALTS THEREOF, THE PIPERAZINO ALKYLAMIDE OF APOLYBASIC ACID AND WATER DISPERSIBLE SALTS THEREOF, AND THE PIPERAZINOAMIDE OF A POLYBASIC ACID AND WATER DISPERSIBLE SALTS THEREOF, THE ACYLRADICAL OF SAID POLYBASIC ACID CORRESPONDING TO THE FORMULA